first of all I have to thank all people that tried to help me in my "losing frames" problems (mainly mpack and shabubu).
I've read some guides for video capturing, and in one of them (about using virtualdub) was written to look in the options for the card driver and not for the WDM, which is buggy and gives problems.
I looked in the options and found only the last one, not the ati card.
I also looked in control panel -> multimedia -> peripherals -> capture device, same thing.
I then uninstalled the drivers and installed the old ones from the cd that came with the card (they were together with mmc 6.3, don't remember the ver) and surprise! the card was displayed everywhere and it seems I have a lot less problems in capturing!
The problem happens to me with the drivers currently in ati site (wme_r128_4_13_7192) and the ones that were there before.